I absolutely love that song. And John Lennon is/was so amazingly cool. *cries* Why did he have to die? It's so sad...
Reference used: http://udel.edu/~mm/beatles/ (Click on the "John" link)
The signature at the bottom of the reference pic is John Lennon's. It's a self-portrait of him.
I'll probably come back and do some more on this later...